Dialogare: compendio di biologia

The compendium collects the basic themes of biology in a very simplified form, ideally following the programmatic criteria of secondary school. The didactic program is articulated starting from the molecules that make up living organisms to end at the theoretical basis of ecology and environmental protection. All the main topics of life sciences such as genetics, anatomy and the evolution of organisms are addressed, always trying to convey the heart of the theoretical concept through a simple but adequate terminology. The goal is to offer a first look at the basis of biology to those who intend to carry out an in-depth study of this subject, which is extremely fascinating but also decidedly complex, vast and multifaceted

Effect of Starvation on the Feeding Activity Toward Sugary Food in the Ant Tapinoma nigerrimum (Nylander, 1856)

In this study, we investigated the effect of starvation on the feeding behavior of the ant Tapinoma nigerrimum. In particular, we tested the response of ants that had experienced different levels of starvation, toward sucrose solutions of increasing concentration. As expected, starved ants promptly reacted to the sugary food sources with a higher rate of acceptance as compared to satiated ones. Acceptance increased both with sugar concentration and the length of the starvation period. However, a consistent fraction of the starved ants did not feed on the solutions, suggesting that starvation had different effects on different individuals, even though they all had food ad libitum before the beginning of the tests, had comparable body sizes, and were collected from the same trail. The different acceptance of sugary solutions may be, therefore, merely because ants fed on the experimental food at different times. Interestingly, in all the experimental groups, ants appeared to satiate quickly, irrespective of the solution tested and fasting duration. This would suggest that the rate of ingestion was independent of these factors, a result partially at odds with previous studies. This study is one of the few ones dealing with the behavioral response of an ant species to a famine event

The Effect of the Introduced Red Wood Ant Formica paralugubris on the Frequency of Ant Nests and First Plesiobiotic Association between Myrmica ruginodis (Nylander, 1846) and Lasius flavus (Fabricius, 1782)

Red wood ants are ecologically dominant species that affect the composition of the invertebrate community. In the past century, one of these species, Formica paralugubris (Seifert 1996), was introduced outside its native area (the Alps), in the Apennines (Italy). Here we investigated the effect of the presence of an introduced population of F. paralugubris on the frequency of nests of other ant species in Abetone, Central Apennines. Ant nests were found only in the area unoccupied by F. paralugubris. In this area, we also found one pleometrotic association between queens of Lasius flavus (Fabricius, 1782) and two plesiobiotic associations, one between Formica fusca (Linnaeus, 1758) and L. flavus and the other one between Myrmica ruginodis (Nylander, 1846) and L. flavus. This latter is the first plesiobiotic relationship reported between these two species, the second reported for M. ruginodis and the 10th for L. flavus. Additionally, this is the first plesiobiotic association reported for the Mediterranean region and Southern Europe

Palatability of glyphosate in ants: a field experiment reveals broad acceptance of highly polluted solutions in a Mediterranean ant

Glyphosate is a systemic herbicide still used in many countries, though there are several known detrimental effects on animals. Previous studies concerning its effects on social insects are available, but they are primarily focused on honeybees; little is known about the interactions of this compound with ants. Here, we assessed whether different concentrations of glyphosate can be perceived by ant workers and to what extent. As a model species, we used the Mediterranean ant Crematogaster scutellaris, commonly found in agroecosystems. We performed 3000 individual tests of acceptance using ten different solutions of various concentrations of the herbicide. Half of the solutions contained added sucrose in order to test the possible masking effect of the sugar taste on glyphosate. We used comparable glyphosate concentrations to those previously used in other studies on social insects or suggested by the producer. We found that the acceptance of the solutions decreased as the concentration of the herbicide increased. However, a significant percentage of ants drank the solutions with concentrations up to dozens of times higher than those inducing toxic effects in bees. In light of these results, we urge further assessment of the effects of glyphosate on ants, particularly because the food ingested by workers is transferred to the brood and queens, posing a potential threat to the health of the entire colony. Surprisingly, we did not record any difference in acceptance between solutions with and without sugar; this point is discussed regarding drought stress.info:eu-repo/semantics/publishedVersio

Sub-lethal doses of imidacloprid alter food selection in the invasive garden ant Lasius neglectus

Despite several restrictions to their use, neonicotinoid insecticides are still widely employed worldwide. Residual sub-lethal amounts of these chemicals can have detrimental effects on the behavior of non-target insects. Toxic effects on economically important species such as bees have been widely documented, but less is known about their toxic action on other social insects, such as ants. In this study, we assessed the effect of different sub-lethal doses of the neonicotinoid imidacloprid on the ability of colonies of the invasive ant Lasius neglectus to select the most profitable resource. We used Y-shaped mazes having an imidacloprid-polluted or an unpolluted sucrose solution on the two branches. Two sucrose (0.1 M, 0.5 M) and two imidacloprid (1 μg/ml, 10 μg/ml) concentrations were used. In parallel, we evaluated the marking activity of foragers who fed on the same solutions. We found that the 0.1 M sugar solution polluted with 1 μg/ml imidacloprid was significantly more frequently selected in binary choices experiments than the unpolluted resource. Moreover, the ingestion of the same combination of sugar and imidacloprid significantly increased the marking rate of foragers. The higher concentration of the pollutant had lower effects, probably because of the hormesis phenomenon. Results suggest that the lower sub-lethal dose of imidacloprid can lead ants to select again the polluted resource. This “active” selection of the pollutant may magnify the negative effects on the colonies. Due to their ecological role, any impairment of ant survival or behavior may have detrimental cascade effects on the whole ecosystem.info:eu-repo/semantics/publishedVersio

Spatial variation of the aggressive response towards conspecifics in the ant Crematogaster scutellaris (Hymenoptera Formicidae)

In this study we investigated the relationship between spatial distance and intraspecific aggression in the Mediterranean tree-nesting ant Crematogaster scutellaris. Aggression tests were carried out in the field confronting group of workers (20 from each nest) collected from pairs of nests located at increasing distances one from the other (5, 10, 20, 40 and 80 meters). For each distance, 6 replicate tests, using different pairs of nests, were carried out. The probability of aggression and the time of the first aggressive event were recorded and modelled as a function of the distance between two nests using generalised linear models. Results showed that both the probability of aggression and the time of first attack were correlated to spatial distance in a complex way, having their maximum at intermediate distances between nests. The observed relationship cannot be simply interpreted according to the “dear enemy” or the “nasty neighbour” effects and contains elements in favour of both

Application of CO 2 carbon stable isotope analysis to ant trophic ecology

Stable isotope analysis of animal tissues is commonly used to infer diet and trophic position. However, it requires destructive sampling. The analysis of carbon isotopes from exhaled CO2 is non-invasive and can provide useful ecological information because isotopic CO2 signatures can reflect the diet and metabolism of an animal. However, this methodology has rarely been used on invertebrates and never on social insects. Here, we first tested whether this method reflects differences in δ13C-CO2 between workers of the Mediterranean ant Crematogaster scutellaris (Olivier) (Hymenoptera: Formicidae, Crematogastrini) fed with sugar from beet (C3; Beta vulgaris L., Amaranthaceae) or cane (C4; Saccharum officinarum L., Poaceae). We found that a significant difference can be obtained after 24 h. Consequently, we used this technique on wild co-occurring ant species with different feeding preferences to assess their reliance on C3 or C4 sources. For this purpose, we sampled workers of C. scutellaris, the invasive garden ant Lasius neglectus (van Loon et al.) (Lasiini), and the harvester ant Messor capitatus (Latreille) (Stenammini). No significant differences in their carbon isotopic signatures were recorded, suggesting that in our study site no niche partitioning occurs based on the carbon pathway, with all species sharing similar resources. However, further analysis revealed that M. capitatus, a seed-eating ant, can be regarded as a C3 specialist, whereas L. neglectus and C. scutellaris are generalists that rely on both C3 and C4 pathways, though with a preference for the former. Our results show that this methodology can be applied even to small animals such as ants and can provide useful information on the diets of generalist omnivores.info:eu-repo/semantics/publishedVersio